1. Technical Field
The present disclosure relates to a voltage amplitude limiting circuit in particular, to a voltage amplitude limiting circuit of full differential circuit.
2. Description of Related Art
The amplitude limiting circuit is a common type of analog circuit which can be used to limit the amplitude of an output voltage to prevent an operation voltage from exceeding the allowable voltage range of the system. The clipper circuit is a type of the amplitude limiting circuit, which is mainly used to selectively modify an output waveform and can remove the portion of the voltage waveform that have exceeded the predetermined voltage level without effecting the remaining voltage waveform.
The most commonly seen limiting circuit is consisted of resistors and non-linear components, wherein the non-linear components are for example, diodes. Diodes have the built-in forward turn-on voltage characteristic, and when the forward-biased voltage is greater than the forward turn-on voltage of the diode, the diode turns on. Placing the resistors and the diode in series, the circuit functions as a limiting circuit and can limit the voltage level of the output voltage waveform within the built-in voltage level of the diode. Wherein using a plurality of diodes in series, the size of the output voltage level limit can be adjusted.
In a voltage amplitude limiting circuit of a full differential circuit, a circuit formed by two diodes disposed in opposite directions and a differential amplifier can function as an amplitude limiting circuit. The above mentioned designed method may have the benefits of circuitry simplicity and low cost, however, the amplitude limiting levels can not be adjusted arbitrarily. Further, since diodes are non-linear electronic components and the linearity of the circuit becomes worse as the voltage level becomes closer to the forward turn-on voltage of the diodes (in series).